Summary

Multiple Cisco products are affected by a vulnerability involving the Open Shortest Path First (OSPF) Routing Protocol Link State Advertisement (LSA) database. This vulnerability could allow an unauthenticated attacker to take full control of the OSPF Autonomous System (AS) domain routing table, blackhole traffic, and intercept traffic.

The attacker could trigger this vulnerability by injecting crafted OSPF packets. Successful exploitation could cause flushing of the routing table on a targeted router, as well as propagation of the crafted OSPF LSA type 1 update throughout the OSPF AS domain.

To exploit this vulnerability, an attacker must accurately determine certain parameters within the LSA database on the target router. This vulnerability can only be triggered by sending crafted unicast or multicast LSA type 1 packets. No other LSA type packets can trigger this vulnerability.

OSPFv3 is not affected by this vulnerability. Fabric Shortest Path First (FSPF) protocol is not affected by this vulnerability.

Affected Products

Vulnerable Products

The following Cisco Products have an OSPF implementation that is affected by this vulnerability. Refer to the Software Versions and Fixes section for information on fixed software.

Cisco IOS Software

Cisco devices that are running Cisco IOS Software and configured for OSPF are vulnerable. Devices that do not have OSPF enabled are not affected by this vulnerability.

Note: This vulnerability can only be triggered by targeting the OSPF multicast address or directly targeting interfaces that are OSPF enabled.

OSPFv3 is not affected by this vulnerability. Fabric Shortest Path First (FSPF) protocol is not affected by this vulnerability.

To determine if a Cisco IOS device is configured with OSPF on an interface, use the show ip ospf interface command. The following is the output of the show ip ospf interface command on a Cisco IOS device configured with OSPF and enabled on the GigabitEthernet0/0/1 interface:

This vulnerability only affects Router LSAs (LSA type 1). As the result of exploitation of this vulnerability, the targeted router will have inconsistent information in its Router Link States LSA database, where the Link ID information will not match Advertising Router ID in the output of the showip ospf database command.
The following is the output of the show ip ospf database command in a Cisco IOS device affected by this vulnerability:

Note: An affected targeted router will propagate the crafted LSA throughout the OSPF area. If the vulnerability is successfully exploited, all the routers in the same OSPF area will have a copy of the crafted LSA Type 1 entry in the OSPF LSA database.

To determine the Cisco IOS Software release that is running on a Cisco product, administrators can log into the device and issue the show version command to display the system banner. The system banner confirms that the device is running Cisco IOS Software by displaying text similar to "Cisco Internetwork Operating System Software" or "Cisco IOS Software." The image name displays in parentheses, followed by "Version" and the Cisco IOS Software release name. Other Cisco devices do not have the show version command or may provide different output.

The following example identifies a Cisco product that is running Cisco IOS Software Release 15.0(1)M1 with an installed image name of C3900-UNIVERSALK9-M:

Cisco devices that are running Cisco ASA or Cisco PIX Software and configured for
OSPF are vulnerable. Devices that do not have OSPF enabled are not
affected by this vulnerability.

The version of software that is running on a Cisco ASA, Cisco ASA-SM or Cisco Pix security appliances can be determined using the show version command from the CLI.

Cisco Firewall Services Module (FWSM)

Cisco devices that are running Cisco FWSM Software and configured for
OSPF are vulnerable. Devices that do not have OSPF enabled are not
affected by this vulnerability.

The version of software that is running on a Cisco FWSM can be determined using the show version command from the CLI.

Cisco NX-OS Software

Cisco devices that are running Cisco NX-OS Software and configured for
OSPF are vulnerable. Devices that do not have OSPF enabled are not
affected by this vulnerability.

The version of Cisco NX-OS Software that is running on Cisco Nexus 3000, 5000, 6000 and 7000 series devices can be determined using the show version command from the CLI.

Exploiting the vulnerability on a Cisco Nexus device will not affect the local routing table of Cisco Nexus. However, the Cisco Nexus devices will install and propagate the crafted LSA to other devices in the OSPF area. Such crafted LSA propagated to other routers that are part of the same OSPF AS may affect the routing tables across the OSPF AS.

Note: Cisco Nexus 1000v Series is not affected by this vulnerability.

Cisco ASR 5000

Cisco devices that are running Cisco StarOS Software and configured for
OSPF are vulnerable. Devices that do not have OSPF enabled are not
affected by this vulnerability.

The version of software that is running on a Cisco ASR 5000 can be determined using the show version command from the CLI.

Products Confirmed Not Vulnerable

The following Cisco products are not affected by this vulnerability:

Cisco IOS XR Software

Cisco Connected Grid Routers

Cisco Nexus 1000v Series

Cisco Next Generation Wiring Closet (NGWC)

No other Cisco products are currently known to be affected by this vulnerability.

Details

OSPF is a routing protocol defined by RFC 2328. It is designed to manage IP routing inside an AS. OSPF packets use IP protocol number 89.

Multiple Cisco products are affected by a vulnerability involving the Open Shortest Path First (OSPF) Routing Protocol Link State Advertisement (LSA) database. This vulnerability could allow an unauthenticated attacker to take full control of the OSPF Autonomous System (AS) domain routing table, blackhole traffic, and intercept traffic.

The attacker could trigger this vulnerability by injecting crafted OSPF packets. Successful exploitation could cause flushing of the routing table on a targeted router, as well as propagation of the crafted OSPF LSA type 1 update throughout the OSPF AS domain.

To exploit this vulnerability, an attacker must accurately determine certain parameters within the LSA database on the target router. This vulnerability can only be triggered by sending crafted unicast or multicast LSA type 1 packets. No other LSA type packets can trigger this vulnerability.

OSPFv3 is not affected by this vulnerability. Fabric Shortest Path First (FSPF) protocol is not affected by this vulnerability.

Network devices running the OSPF protocol may be impacted by this vulnerability if they receive a crafted LSA type 1 packet. This packet does not have to be acknowledged, and it can originate from a spoofed IP address.
In order to exploit this vulnerability, an attacker needs to determine a number of factors, such as the network placement and IP address of the target router, LSA DB sequence numbers, and the router ID of the OSPF Designated Router (DR). An attacker needs to know all of the factors in order to exploit this vulnerability.

Since OSPF processes unicast packets as well as multicast packets, this vulnerability can be exploited remotely and can be used to target multiple systems on the local segment simultaneously. Using OSPF authentication as described in the Workarounds section can mitigate the effects of this vulnerability. Using OSPF authentication is a highly recommended security best practice, regardless of the presence of this vulnerability.

Once processed, a crafted LSA type 1 packet may cause a directly targeted router to flush the content of its routing table and propagate the crafted LSA update throughout the OSPF area. OSPF member routers of the same area would be affected by processing and installing a crafted LSA type 1 packet propagated by the victim router. This may lead to a number of consequences, such as the injection of false routes into the OSPF routing table, the blackholing of traffic, or redirecting of traffic to a destination that is controlled by an attacker.

In order to recover affected systems, administrators can delete the OSPF configuration from the affected device and enable it again. Alternatively, a reload is required to recover affected systems. Clearing the OSPF process or routing table by means of commands such as clear ip ospf process or clear ip route does not have any effect and can not be used to recover affected systems.

Workarounds

The use of OSPF authentication is a valid workaround. OSPF packets without a valid key will not be processed. MD5 authentication is highly recommended, due to inherent weaknesses in plain text authentication. With plain text authentication, the authentication key will be sent unencrypted over the network, which can allow an attacker on a local network segment to capture the key by sniffing packets.

Additionally, an OSPF Time To Live (TTL) security check can be applied as a partial workaround. Note: This workaround is valid to protect against remotely triggered attacks and does not protect against attackers that are layer 2-adjacent to vulnerable devices.

Fixed Software

When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Notices archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

Cisco IOS Software

Each row of the following Cisco IOS Software table corresponds to a Cisco IOS Software train. If a particular train is vulnerable, the earliest releases that contain the fix are listed in the First Fixed Release column. The First Fixed Release for All Advisories in the March 2013 Bundled Publication column lists the earliest possible releases that correct all the published vulnerabilities in the Cisco IOS Software Security Advisory bundled publication. Cisco recommends upgrading to the latest available release where possible.

Cisco FWSM Software

All versions of Cisco FWSM Software are affected by the vulnerability that is disclosed in this document. There are currently no official fixed releases available on Cisco.com, but interim releases may be available through Cisco Technical Assistance Center (TAC).

Customers with service contracts should contact Cisco support organization per the instructions in the Obtaining Fixed Software section of this advisory.

Cisco NX-OS Software

Cisco Nexus 7000:

Affected Releases

First Fixed Release

4.x

Vulnerable

5.x

Vulnerable

6.0

Vulnerable

6.1

6.1(4)a

6.2

6.2.6

7.x

Not vulnerable

Cisco Nexus 5000:

Affected Releases

First Fixed Release

4.x

Vulnerable

5.x

Vulnerable

6.x

Vulnerable

7.x

7.0.0.N1(1)

All versions of Cisco NX-OS Software for Cisco Nexus 3000, Cisco Nexus 4000, Cisco Nexus 6000, and Cisco Nexus 9000 are affected by the vulnerability that is disclosed in this document. There are currently no official fixed releases available on Cisco.com, but interim releases may be available through Cisco Technical Assistance Center (TAC). Customers with service contracts should contact Cisco support organization per the instructions in the Obtaining Fixed Software section of this advisory.

Cisco StarOS Software

This vulnerability has been fixed in Cisco StarOS Software version 14.0.50488.

Customers with service contracts should contact Cisco support organization per the instructions in the Obtaining Fixed Software section of this advisory.

Exploitation and Public Announcements

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

This vulnerability was found and reported to Cisco by Dr. Gabi Nakibly from Rafael Advanced Defense Systems as joint work he conducted with Eitan Menahem, Yuval Elovici and Ariel Waizel of Telekom Innovation Laboratories at Ben Gurion University.

Cisco Security Vulnerability Policy

To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

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Cisco Security Vulnerability Policy

To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.